FIG. 1 is a schematic sectional view of a typical nitride semiconductor light emitting device.
Referring to FIG. 1, a typical nitride semiconductor light emitting device includes a buffer layer 11, an n-type nitride layer 12, an activation layer 13 of a multi-quantum well structure, and a p-type nitride layer 14, which are sequentially stacked on a sapphire substrate 10. In addition, a p-side electrode 15 is formed on an upper surface of the p-type nitride layer 14 and an n-side electrode 16 is formed on an exposed surface of the n-type nitride semiconductor layer 12.
The nitride semiconductor light emitting device emits light through recombination of electrons and holes in the activation layer 13.
To improve luminous efficiency of the activation layer 13, various studies have been actively carried with the goal of improving light extraction efficiency, i.e., improving internal quantum efficiency and external quantum efficiency.
Improvement of internal quantum efficiency is generally achieved through improvement of luminous efficiency of light generated in the activation layer, as disclosed in Korean Patent Laid-open Publication No. 10-2010-0037433 (Apr. 9, 2010).
On the other hand, as the area of the nitride semiconductor light emitting device increases, it becomes difficult to achieve uniform current spreading. As a result, leakage current increases between the n-type nitride semiconductor layer and the buffer layer in the nitride semiconductor light emitting device. Such increase in leakage current provides low current density in the activation layer, causing deterioration of internal quantum efficiency.